mono rail staircase construction

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Hey all right so a long story short is i've got a load of U-profiles from a bankrupcy and intend to use them to make a mono rail staircase.I studied welding/construction in belgium but its been a good 7 years since then, combine that with fluxuating electricity supply to my welder(It's like someone is playing with your power setting all the time) and i'm not confident my welds will be estheticly pleasing enough to be exposed.Hence in this design the welds are for the most part hidden.My main concern is warping, I've never welded big U-profiles like this and am not sure how severe things will warp.also i've designed jigs to hold the metal contraptions for each step in place to prevent it from moving. i'll attach images of those aswell.any and al advice would be much appreciated, i'll most likely be buying materials this week.I'm pretty exited to get stuck into some metalwork again after all this time, i used to really enjoy it.I'll put titles of some annotated images+links to them here(note if you hold Ctrl while clicking all of these in succession that will open each image in a seperate tab of your browser, also you may want to click on the image in the link to zoom in):overview of the metal construction:http://imageshack.us/f/191/overviewlz.jpg/zoomed in view of a single step and its three welds shown in black:http://imageshack.us/f/232/singlestep.jpg/Connection under the landing as seen from below:http://imageshack.us/f/15/connectionunderlanding.jpg/dimensions of the U-profile:http://imageshack.us/f/834/uprofilesize.jpg/overview top U-profile(landing to top floor) construction:http://imageshack.us/f/121/landingtotopfloorgirder.jpg/1 of 2 jigs for step assembly:http://imageshack.us/f/135/jig1forstep.jpg/2 of 2 jigs for step assembly:http://imageshack.us/f/62/jig2forstep.jpg/thanks
Reply:[QUOTE=Sir;536741]Hey all  and i'm not confident my welds will be estheticly pleasing enough to be exposed.what makes you think they are strong enough for a structure that people will walk  on? afluctuating power supply  does not inspire confidence in the weld............
Reply:Hey weldbead, thx for your reply.I'm confident they will be;Although i have the fluxuating power supply, i'll weld at night so hopefully that way i'll have the towns power to myself, aside from that if a weld messes up i will grind it out and redo it.although its been a while since i spent alot of time welding i've gotten certificates for almost al of these welds(not the little one at the top left of the image of the single step but thats pretty straightforward and the weld is overkill there anyway) in the past and they're all relatively simple positions.
Reply:from what i can see your stairs are straight runs without any curves.  the welding all takes place on the web or back of the channel.  I am assuming that the "U-profile" is a standard channel.  any distortion you create will be bending the stair stringer in a gentle concave curve.   It will be easy to heat shrink it straight by heating to red the toes of the channel every few feet.If you are concerned you might tack weld the stair assemblies on both stair stringers then tack weld the stringers back to back with toes touching.  Weld all your stairs, let cool , then break the tack welds to separate the stringers.
Reply:hey lotechman thanks alot for your advice.I'm afraid heating the "toes" isn't an option easily available to me as I dont have an oxygen acetyleen setup(i really wish i did) so i'll have to go with the tacking option. is this roughly what you mean? http://img121.imageshack.us/img121/4...loorgirder.jpg(by the way i have some extra U-profile in stock so i'm able to tack that on)Last edited by Sir; 07-26-2011 at 04:08 PM.
Reply:Your drawing is exactly what I would suggest except for a few minor adjustments.   You do not need as many tabs welded across.  Stand the tabs on edge when you weld them and only put a fillet on one side.  When cool all you have to do is hit each tab with a hammer to break them off.   Consider putting a shim in the middle across and between the toes.  I am guessing at 1/2 inch to a full one inch of thickness.  This will prevent springing action when the tabs are removed.   Hopefully it springs to flat.    It is hard to estimate just how much you will need.  I am guessing 3/4 inch but there are so many variables.  You don't know how much residual stress in the channels was in there before you start welding.   Sometimes you don't get exactly what you want....  I often jokingly comment that I should have sacrificed a chicken before I started  LOLSomething I totally forgot!!  You MUST use a full penetration weld at the joint connecting the landing.  Bevel the edges and weld the inside profile first.  Take a grinder and vee the opposite side down until you reach sound metal then fill with weld...  that brace is important on each stringer.  For some reason in my career that is the primary location for inspection.  They will build a multi storied building and only X-ray the landing to stringer connections.Last edited by lotechman; 07-26-2011 at 07:07 PM.
Reply:Hey lotech thanks a lot man this is quality stuff,So in terms of the tabs and shim's is this what you meant?:http://img705.imageshack.us/img705/4...loorgirder.jpgAlso, i'm confused as to bracing when i come to weld the U-profiles together, i'm guessing i'll need to brace that with a different but similar set up to keep it from going boomerang.also i'm looking at welding the straight connection in thesame way you suggested "full penetration weld at the joint connecting the landing"I'm going to start cutting some of the u-profile today, its going to be tedious as i've only got a big angle grinder to help me with them but that said its only 10 cuts.Thanks again for all this advice lotech, I'll be cooking chicken tonight
Reply:No put one shim or bar in the middle and clamp the ends so that they touch.  In effect you have made an opposite boomerang.  That is exactly right about the tabs.  It makes it so much easier when taking apart.  Some people also take a piece of flat bar about a foot long and tack weld that to the toe of the channel across where the joint is when they do a a straight connection.  That prevents the channel taking a bend at the joint.